Optical Illusions

HOLLOW IN THE FACE ILLUSION

LILAC CHASER

If the image is not displayed, go to http://www.vision-and-eye-health.com/images/LilacChaser.gif It consists of 12 lilac (or pink or magenta-like), blurred disks arranged in a circle (like the numbers on a clock), around a small, black, central cross on a grey background. One of the disks disappears briefly (for about 0.1 second), then the next (about 0.125 second later), and the next, and so on, in a clockwise direction. When one stares at the cross for about 20 seconds or so, one first sees a gap running around the circle of lilac disks, then a green disk running around the circle of lilac disks, then a green disk running around on the grey background, the lilac disks appearing to have disappeared or to have been erased by the green disk.

ADELSON’S CHECKER SHADOW ILLUSION

The image shows what appears to be a black and white checker-board with a green cylinder resting on it that casts a shadow diagonally across the middle of the board. The black and white squares are actually different shades of gray. The image has been constructed so that “white” squares in the shadow, one of which is labeled “B,” are actually the exact same gray value as “black” squares outside the shadow, one of which is labeled “A.” The two squares A and B appear very different as a result of the illusion.

MOTION ILLUSION

A static image appears to be moving due to the cognitive effects of interacting color contrasts and shape position. Click on images for a better view.

LEANING TOWER ILLUSION

The two images above are identical, yet the tower on the right appears to be leaning more steeply. The reason for this is because the visual system treats the two images as if part of a single scene.

COLOR PERCEPTION/BEZOLD EFFECT

A color may appear different depending on its relation to adjacent colors. Believe it or not – the pink spots in the image above are the same – if you don’t believe me, open the image in photoshop and compare them.

WHITE ILLUSION

The same target luminance can elicit different perceptions of brightness in different contexts. Note, that although the gray rectangles are all of equal luminance, the ones seen in the context with the dark stripes appear brighter than the ones seen in the context with the bright stripes.

HERMANN GRID ILLUSION

The illusion is characterised by “ghostlike” grey blobs perceived at the intersections of a white (or light-colored) grid on a black background. The grey blobs disappear when looking directly at an intersection.

INVERSE IMAGE

Stare at the center of the image above for about 30 seconds then immediately look at a blank white wall or a piece of white paper. Stare at the blank paper and an image will emerge. The more you stare, the clearer the image becomes.

INSTANT GRATIFICATION

Stare at the dot in the center of the image and move your head back and forth – the rings will rotate.

STRAIGHT LINES/CAFE WALL ILLUSION

This optical illusion makes the parallel straight lines appear to be bent. To construct the illusion, alternating light and dark “bricks” are laid in staggered rows. The images above are composed entirely of straight lines. If you don’t believe, try using a ruler to test it.

ZOLLNER ILLUSION

In this figure the black lines seem to be unparallel, but in reality they are parallel. The shorter lines are on an angle to the longer lines. This angle helps to create the impression that one end of the longer lines is nearer to us than the other end.

MONSTER MAGIC

The two monsters are exactly the same size.

BLIVET

A blivet, also known as a poiuyt, is an undecipherable figure, an optical illusion and an impossible object. It appears to have three cylindrical prongs at one end which then mysteriously transform into two rectangular prongs at the other end.

EBBINGHAUS ILLUSION

An optical illusion of relative size perception. In the best-known version of the illusion, two circles of identical size are placed near to each other and one is surrounded by large circles while the other is surrounded by small circles; the first central circle then appears smaller than the second central circle.

FRASER SPIRAL ILLUSION

Also known as the false spiral, or by its original name, the twisted cord illusion. The overlapping black arc segments appear to form a spiral; however, the arcs are a series of concentric circles.

ISOMETRIC ILLUSION

Also called an ambiguous figure or inside/outside illusion, a type of optical illusion, specifically one due to multistable perception. In the image above, the shape can be perceived as either an inside or an outside corner.